Field of the Invention
The present invention relates to a phasing adder and an ultrasound probe.
Description of Related Art
Conventionally, there is an ultrasound diagnostic apparatus which irradiates ultrasound inside a subject, receives the reflected wave and analyzes the reflected wave to examine an internal structure. With ultrasound diagnosis, it is possible to examine the subject in a non-destructive, non-invasive form, and is therefore used widely for various purposes such as medical examination or internal examination of a building.
In an ultrasound diagnosis apparatus, the received ultrasound is converted to an electric signal according to its intensity and is obtained. In receiving the ultrasound, a transducer such as a piezoelectric element is used. The mechanical deformation (expansion and contraction) of the piezoelectric element by sound pressure of the ultrasound is converted to an electric signal (charge amount) according to the deformation amount and is detected. Here, since there is a difference in the timing that the large number of piezoelectric elements receive the reflected wave from the examination target point, the data regarding the reflected wave from the examination target point can be obtained by setting and adding a delay time suitable for each element.
Lately, consumption of electric power of the ultrasound diagnostic apparatus is increasing because of increase of the number of piezoelectric elements for receiving and increase of a sampling rate of receiving data due to images becoming highly accurate. Japanese Patent No. 4557575 discloses the following technique. An electric signal is selectively input in any CCD (Charge Coupled Device) delay element provided in parallel with each piezoelectric element with a different transfer gate number. Charge data regarding the plurality of piezoelectric elements are delayed a suitable number of steps and added by phasing adding. Then, the above data is converted to voltage data in one of the FGA (Floating Gate Amplifier). With this, it is possible to reduce the number of FGA used on each piece of data before phasing adding from the conventional number and to reduce electric power consumption.
However, the intensity of the electric signal obtained by the transducer according to the intensity of the ultrasound received in ultrasound diagnosis is very small. Therefore, normally such electric signal is amplified right after this is obtained by the transducer and then transferred and processed. Here, if a low noise amplifier (LNA) is used to amplify the signal without increasing the noise level, the supply electric current increases according to the noise reduction amount. Therefore, conventionally, there is a problem that it is difficult to achieve both of the following, enhancing the signal-noise ratio (SNR) and suppressing electric power consumption.